The AAA open world doesn't feel any different here than when I first encountered it in Blood Dragon years ago now. There are good mainline "missions" with actual level design, actual encounter design, some story beats etc. However most of your time is spent using a vehicle (or mount) to traverse between optional generic outposts, small enemy groups or treasure zones. Overly generous fast travel is available once you get bored. I've never found it particularly engaging but it's totally worn out, uninspired game design by this point.
Don't get me wrong Elden Ring is probably about as good as a game made this way can get but these modern open worlds always feel like they've been shat out by an algorithm once you take away the "mainline" content.
At present, not a timeless classic the way the Souls game are. Just a pretty good game. I'll see if my opinion changes as I go further ahead.
I can't think of many open world RPGs that are better than this, honestly. Each area feels distinct, they loop back onto each other in Souls-like fashion (discovering the item that's out of reach in the very first opening area was a great surprise), and at least in the opening areas, there's very little that feels copy-pasta'd. And the sheer scale of things is impressive. You can compare it to the Witcher, for example, but Witcher 3 and most open world games frequently feel like everything is all designed on one flat plane. With Elden Ring, you might spend an hour fighting through one area, only to suddenly loop back onto it a few hours later, only this time from thousands of feet above it. Graphically, the game is a bit janky, which means that I'm not sure that it does immersion into a world as well as some other games (not to mention that it's very much a souls-like, which means that the world is essentially just enemies), but it's incredibly impressive level design. I cannot remember the last game that had exploration that's as rewarding and fun as this.